Metformin For Gestational Diabetes

Gestational diabetes mellitus (GDM) can affect pregnant women, complicating perinatal outcomes and causing health concerns. Between 2% and 10%¹ of pregnant women are impacted by gestational diabetes in the US each year.

The condition occurs when your body doesn’t use insulin properly during pregnancy due to pregnancy hormones, leading to insulin resistance.

You may be able to manage GDM by making changes to your diet and keeping active, but medications like metformin offer additional help in regulating glucose levels. However, metformin is not suitable for everyone, and you might need to take insulin instead.

Learn more about gestational diabetes and whether metformin could be a safe and effective treatment for you.

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We make it easy for you to participate in a clinical trial for Gestational diabetes, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

What is metformin?

Metformin belongs to the biguanide class of antidiabetic drugs. It is approved by the US Food and Drug Administration (FDA) to treat type 2 diabetes.

Doctors may also recommend it to treat other conditions, including polycystic ovarian syndrome (PCOS) and gestational diabetes. However, the drug is not approved to treat these conditions.

Metformin helps control and balance glucose (sugar) levels in your blood. It does this by combating insulin resistance, which occurs when the insulin produced in your body doesn’t work properly.

The drug works in two ways:

  1. Improves insulin sensitivity (where the body cannot use glucose effectively)

  2. Lowers the amount of glucose your liver produces

Metformin may be used alongside insulin and other medications in some cases.

While taking metformin, it’s important to continue taking steps to adopt a healthy lifestyle, for example, by doing more exercise and improving your diet.

What is gestational diabetes?

Gestational diabetes affects up to 10% of pregnant women. Doctors and scientists believe it is caused by placenta hormones that stop insulin from working properly, resulting in insulin resistance.

You might have gestational diabetes without experiencing any signs or symptoms, although some women have increased thirst or urinate more often.

Several factors raise your risk of developing the condition, including a family history of type 2 diabetes, being aged 25 or older, previous gestational diabetes, a previous baby with high birth weight, or a polycystic ovary syndrome (PCOS) diagnosis.

Gestational diabetes complications

Most women with GDM have healthy pregnancies and deliveries. However, without effective diagnosis and treatment, gestational diabetes can cause a number of complications for you and your baby. These include:

Fetal macrosomia

This condition is characterized by abnormally high fetal growth (when a baby weighs more than 4 kg or 4.5 kg at birth).

The condition raises the likelihood of cesarean or instrumental vaginal delivery, challenging vaginal delivery, neonatal hypoglycemia, and fetal birth trauma.


Preeclampsia is characterized by high blood pressure. It increases your risk of seizures, brain injury, kidney and liver problems, and fluid in the lungs.

Untreated, preeclampsia could be life-threatening for you and your baby.

Neonatal polycythemia

This is a blood disorder characterized by a high concentration of red blood cells. It can cause hyperviscosity (slow blood flow), which can lead to organ and tissue damage and an increased risk of seizures and stroke.

Neonatal hypoglycemia

Hypoglycemia means low blood sugar levels. Neonatal hypoglycemia is caused when the mother has poorly controlled diabetes. This causes more sugar to cross the placenta than the baby needs, increasing the amount of insulin in the body. High insulin levels at birth can put the newborn at risk of low blood sugar.


Polyhydramnios occurs when there is too much amniotic fluid. It can increase your risk of early labor and postpartum hemorrhage.

Gestational diabetes may also cause jaundice, premature birth, and stillbirth.

Advantages of metformin for treating GDM

When lifestyle changes are not enough to stabilize blood sugar levels during pregnancy, your doctor may recommend medication. Medication prescribed to treat gestational diabetes is typically insulin or metformin.

Compared to insulin, oral metformin has a number of reported advantages:

  • Metformin can improve your body’s insulin sensitivity, lowering glucose production in the liver while balancing out the body’s responsiveness

  • Metformin costs less

  • Ease of use: you can take metformin as a tablet, so there’s no need for injections

  • Metformin may be safer for the mother as there is a low risk of causing hypoglycemia and high blood pressure

  •  Metformin causes lower maternal weight gain

  • Lower risk of neonatal hypoglycemia and fetal macrosomia

While metformin has advantages, it is not a suitable medication for everyone. Your doctor may advise you that insulin is a more effective treatment for you.

Is metformin safe to take during pregnancy?

Metformin is listed as a pregnancy category B drug, meaning animal reproduction studies have not shown there is a high risk to an unborn fetus. This category also means there are insufficient or low-quality studies examining the effects of the drug in pregnant humans.

The drug is not currently approved by the FDA for gestational diabetes treatment. Without further research and universal approval, you should talk to your doctor about the pros, cons, and potential risks of taking metformin while pregnant.

Metformin is thought to be safe to take while breastfeeding, as the drug enters breast milk in low amounts. Check with your doctor before taking metformin while breastfeeding.

Does metformin cause side effects?

While metformin is thought to be a safe and effective GDM treatment, it does carry the risk of side effects.

The most common side effects reported with metformin are:

  • Stomach pain

  • Decreased appetite

  • Diarrhea

  • Metallic taste

  • Nausea

  • Vomiting

You may be able to prevent or reduce the severity of an upset stomach by eating with or after your metformin dose. If you experience an upset stomach or diarrhea at first, you might find your body adjusts to the drug over time, causing your side effects to ease.

Less common/severe side effects

Metformin may cause more serious side effects, which are less common. These include:

Lactic acidosis

This is usually caused by an overdose or by a gradual accumulation of lactate in the body due to liver or kidney problems.

It can cause:

  • Severe abdominal discomfort

  • Muscle spasms or cramps

  • Decreased appetite

  • Unusual sleepiness

  • A general feeling of weakness

Lactic acidosis can be life-threatening.


Low blood sugar may occur if you take metformin with insulin.

Symptoms include:

  • Feeling hungry

  • Confusion

  • Trembling

  • Shaking

  • Sweating

Vitamin B-12 deficiency

Signs you have vitamin B-12 deficiency include:

  • Muscle weakness

  • Pins and needles

  • Extreme tiredness

  • A red, painful tongue

Get medical help as soon as possible if you develop symptoms of these serious conditions. You should also see a doctor if you have yellowing of your skin or eyes, fast or shallow breathing, a slow heartbeat, or you generally feel unwell.

Is metformin a good choice for you?

Metformin can be an effective treatment for gestational diabetes as well as some other health conditions, but it’s not a suitable choice for everyone. You should only take this medication after discussing it with your doctor.

Ensure your doctor is aware of any other medications or supplements you are currently taking and any diagnosed health conditions that could affect the way the drug works.

Some women need supplemental insulin to treat GDM, and metformin may not be as effective. Studies² have found the following characteristics may limit the efficacy of metformin:

  • History of GDM

  • GDM diagnosed early in pregnancy

  • Older age

  • Higher fasting glucose levels when diagnosed

  • High body mass index (BMI)

  • High baseline blood sugar or serum fructosamine levels

Metformin is not always a full-fledged replacement for insulin and should not be considered a long-term solution for irregular glucose levels.

Studies show that around 70%³ of women diagnosed with GDM will develop long-term type 2 diabetes postpartum. If you’ve taken metformin throughout your pregnancy but your glucose levels begin to stabilize after delivery, your doctor may suggest discontinuing the medication or reducing the dosage. You can then see how your body reacts to the change.

How to take metformin

To reduce your chance of developing side effects and prevent complications, follow all the directions on the prescription label and take the medication as recommended.

If you’re taking a pill form of metformin, avoid crushing, chewing, or breaking the tablet. Take your dose with meals to reduce the risk of an upset stomach, usually two to three times per day.

The liquid form should also be taken with food, usually once or twice per day.

Metformin is also available as an extended-release medication, which can help your body absorb the drug and reduce side effects. This form of the drug is usually taken once per day, preferably in the evenings.

Try to take the medication at the same time each day to help you remember your dose.

Other treatments for gestational diabetes

Other treatments may help stabilize your blood sugar levels and prevent GDM complications if metformin is unsuitable for you.

Other medications

Insulin is one of the most common alternatives to metformin. Your doctor may recommend taking both at the same time.

Another alternative to metformin is glyburide. This medication is similar to metformin, but instead of targeting your liver, it works by helping your pancreas lower blood sugar levels by producing more insulin. 

Glyburide is not usually a first-line treatment.⁴ Compared to metformin, there is less research proving its efficiency. However, it can help manage type 2 diabetes and could be a beneficial option for regulating glucose levels during pregnancy.

Maintaining a healthy weight

Ask your doctor about safe and sustainable ways to reach a healthy weight.

For people who are overweight, losing weight can help manage your blood sugar levels and prevent GDM complications.

Eating a healthy diet

Your doctor will recommend changing your diet to stabilize your blood sugar levels. If this doesn’t work, they may recommend taking metformin while following a healthy diet plan.

Eating plenty of lean proteins, fruits, and vegetables can help control your blood sugar levels. Your doctor will also tell you to limit your intake of fat and sugar.

If you need advice on which foods to eat as part of a healthy diet, ask your doctor to refer you to a dietitian.

Keeping active

Exercising regularly helps stabilize blood sugar levels by encouraging your body to use glucose more effectively. It can also help you maintain a healthy weight.

Check with your doctor before starting a new exercise regime to ensure it’s safe for you and your baby.

The lowdown

Metformin can be used to treat gestational diabetes, a condition that affects pregnant women and can cause serious complications.

Although the medication is not FDA-approved for this purpose, it has been shown to offer many benefits, including lowering the risk of hypoglycemia (in the mother and baby), high birth weight, and hypertension. It is also more cost-effective than insulin and easier to use.

Metformin can be taken as a standalone medication or paired with other drugs like insulin.

Research into the safety of metformin during pregnancy is limited, but it is generally accepted to be safe. Like all medications, it can cause side effects, including nausea, vomiting, and diarrhea.

When compared to relying solely on a healthy diet and active lifestyle, metformin shows positive results in improving neonatal outcomes. However, metformin is not a quick solution for GDM, so you should still prioritize leading a healthy lifestyle.

Have you considered clinical trials for Gestational diabetes?

We make it easy for you to participate in a clinical trial for Gestational diabetes, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

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